Just an update on this -
I bought and downloaded the Gibson EB-5 string Bass from Cakewalk.
It installed into Rapture (though the Expansion Pack said Dimension Pro). and when
selecting it in Rapture, I got the message 'Error uncompressing data - Program Load failed'.
Having read other posts about EB5 I was prepared for this.
So I located the installed EB5 folders under Rapture, and copied them to the
corresponding directories under Dimension Pro. After a VST rescan and an
'F5' in the DimPro browser, everything was working beautifully.
So, a happy ending for me, thanks to this forum, of course. :-)